题型:阅读理解 题类:常考题 难易度:普通
江西省赣州市2017-2018学年高一下学期英语期末考试试卷
Think of a seed buried in a pot. It's dark down there in the potting soil. There's no light, no sunshine. So how does it know which way is up and which way is down? It does know. Seeds send shoots up toward the sky, and roots the other way. Darkness doesn't confuse them. Somehow, they get it right.
More surprisingly, if you turn a seedling (秧苗) or a whole bunch of seedlings upside down, as Thomas Andrew Knight of the Royal Society did around 200 years ago, the tips and roots of the plant will sense, “Hey, I'm upside down. Look! I. will turn my way to the right direction and do a U-turn.”
How do they know? According to botanist Daniel Chamovitz, Thomas Knight about 200 years ago guessed that plants must sense gravity. Knight proved it with a crazy experiment involving a spinning plate.
He attached a bunch of plant seedlings onto a disc. The plate was then turned by a water wheel powered by a local stream at a speed of 150 revolutions (旋转) per minute for several days.
If you have been at an amusement park in a spinning teacup, you know that because of centrifugal force (离心力) you get pushed away from the center of the spinning object toward the outside.
Knight wondered, would the plants respond to the centrifugal pull of gravity and point their roots to the outside of the spinning plate? When he looked, that's what they'd done. Every plant on the disc had responded to the pull of gravity, and pointed its roots to the outside. The roots pointed out, and the shoots pointed in. So Thomas Knight proved that plants can and do sense the pull.
Welcome to the Electronic Village to explore new ways of language teaching and learning.
Electronic Village Program (Thursday, June 18, 2015) | |
Nearpod ❖9:00 am to 10:00 am ❖Room 501 Nearpod is a software program that creates a rich context (语境) for students to learn vocabulary. The presenter will show how to use it. | TEO ❖ 2:00 pm to 3:00 pm ❖Room 502 Our students come from different backgrounds but have the same desire to learn on-line. The presenter will use examples from his first on-line class to explain how any teacher can begin teaching on-line with TEO. |
Kahoot ❖10:30 am to 11:30 am ❖ Room 601 Kahoot software can be used to create grammar tests which can be graded on a network. It can provide students with instant feedback (反馈), including reports about their strengths and weaknesses. | Prezi ❖3:30 pm to 4:20 pm ❖Room 602 Uses of Prezi in listening and speaking courses draw students' attention to speaking more fluently. The presenter will show how students can use Prezi to confidently present on a variety of topics, including introducing family, friends, and hobbies. |
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